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Hydrologic Units Maps of the Conterminous United States for the EPA Clean Air Mapping and Analysis Program (C-MAP)
Entry ID: HUC250k

Abstract: The Geographic Information Retrieval and Analysis System (GIRAS) was
developed in the mid 70s to put into digital form a number of data layers which
were of interest to the USGS. One of these data layers was the Hydrologic
Units. The map is based on the Hydrologic Unit Maps published by the U.S.
Geological Survey Office of Water Data Coordination, together with the list
descriptions and name of ... View entire text
Related URL
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Geographic Coverage
Spatial coordinates   
  N: 48.29   S: 22.87   E: -65.32   W: -127.91

Data Set Citation
Dataset Originator/Creator: Steeves, Peter and Douglas Nebert
Dataset Title: Hydrologic units maps of the Conterminous United States
Dataset Release Date: 1994-01-01T00:00:00.000Z
Dataset Release Place: Reston, Virginia
Dataset Publisher: USGS
Version: Not provided
Data Presentation Form: maps
Online Resource:
Temporal Coverage
Start Date: 1970-01-01
MAPS Ancillary Description
Quality The data produced by the Geographic Information Retrieval and Analysis System
(GIRAS) was originally collected at a scale of 1:250K. Some areas, notably
major cities in the west, were recompiled at a scale of 1:100K. In order to
join the data together and use the data in a geographic information system
(GIS) the data were ... View entire text
Use Constraints These data were digitized at a scale of 1:250,000 with some portions of
coverage at 1:100,000- and 1:2 million scale. Limitations of the data strictly
revolve around this scale input. Use of these boundaries with larger scale data
(i.e. 1:24k hydrography) is not recommended as it would be beyond the
resolution capabilities of the data set.
Data Set Progress
Data Center
Clean Air Markets Division, U.S. Environmental Protection Agency Supplemental Info
Data Center URL:

Data Center Personnel
Phone: 202-564-9180
Email: camdgis at
Contact Address:
Clean Air Markets Division
1200 Pennsylvania Avenue, NW
Mail Code 6204J
City: Washington
Province or State: DC
Postal Code: 20460
Country: USA
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Distribution Media: ftp
Distribution Format: ArcInfo export format
Fees: No fees

Distribution Media: ftp
Distribution Format: SDTS
Fees: No fees
Phone: (301) 614-6898
Fax: 301-614-5268
Email: Tyler.B.Stevens at
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory
City: Greenbelt
Province or State: MD
Postal Code: 20771
Country: USA
Extended Metadata Properties
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Creation and Review Dates
DIF Creation Date: 2002-11-21
Last DIF Revision Date: 2018-07-26